Fix Docker build: Add Pillow dependencies and correct Python path

[Copilot]

Docker build failing on Pillow compilation due to missing JPEG libraries. Additionally, multi-stage build copying from wrong Python version path.

Changes

Builder stage dependencies

• Add jpeg-dev zlib-dev for Pillow compilation

Runtime stage dependencies

• Add libjpeg for Pillow JPEG support

Multi-stage build path

• Fix python3.9 → python3.14 in COPY directive

# Builder stage
RUN apk add --no-cache \
    gcc g++ make musl-dev libffi-dev \
+   jpeg-dev zlib-dev \
    pango gdk-pixbuf cairo gobject-introspection-dev

# Runtime stage
RUN apk add --no-cache \
+   libjpeg \
    pango gdk-pixbuf cairo gobject-introspection

# Copy from builder
-COPY --from=builder /usr/local/lib/python3.9/site-packages /usr/local/lib/python3.9/site-packages
+COPY --from=builder /usr/local/lib/python3.14/site-packages /usr/local/lib/python3.14/site-packages

Original prompt

Reference: https://github.com/slehee/PNPT-Prep/actions/runs/20876993034/job/59987825997

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